PB2052: THE HEMATOLOGICAL SIDE OF TNFRSF13B/TACI: A MONOCENTRIC EXPERIENCE
Authors: Andrea Beccaria, Marina Lanciotti, Maria Carla Giarratana, Elena Palmisani, Isabella Ceccherini, Alice Grossi, Roberta Caorsi, Marco Gattorno, Paola Terranova, Michela Lupia, Domenico Coviello, Massimo Maffei, Sabrina Zanardi, Maurizio Miano, Carlo Dufour, Francesca Fioredda
Journal: HemaSphere (2023)

Topic: 12. Bone marrow failure syndromes incl. PNH - Clinical Background: TNFRSF13B/TACI is the most common molecular defect related to Common Variable Immunodeficiency Disorders (CVID) which represents a heterogeneous group of diseases characterized by antibody deficiency and very low isotype switched memory B cell in the peripheral blood and variable clinical phenotype (ierecurrentinfections, lymphoprolipheration and autoimmune cytopenia) While this disorder is surely well recognized by the immunologists, it could probably a bit underestimated within the hematological setting. Aims: To describe the frequency of TNFRSF13B/TACI in a hematological population seen at a single center mainly for autoimmune cytopenia, ALPS/ALPS like disorders (NIH 2009 criteria) or in hypogammaglobulinemia with autoimmunity. Methods: All patients with the above diagnosis, studied with an Next Generation Sequencing (NGS) panel of 162 genes, including TNFRSF13B/TACI variant were considered eligible for the present study. Clinical, biochemical, immunological and genetic data were retrieved from our Cytopenia/ALPS Registry Results: From 2015 to 2022 at Unit of Hematology of Giannina Gaslini Children Hospital, 305 patients were screened with the estended NGS panel. A total of 28 subjects (43% females) affected with predominant feature of cytopenia 14(57%), ALPS/ALPSlike syndrome 9 (28%) or with a highly suspicion of CVID phenotype 5(18%) with median age at at our first observation of 10 years (0.1-48 yrs) were carriers of TACI variants (Table 1). As for the genetic definition according to Clin Var, 6/28 (21.5%) were P/LP, 6/28 (21.5%) were VUS and the remaining 16/28 (57%) were TACI variants with Conflicting Interpretation Results. Overall in 9/25 (36%) subjects, immunology was completely normal: neither depletion of immunoglobulins or lymphocyte count reduction were observed. This silent immunulogical aspect was observed in 50% of the cytopenic subjects and in 43% of ALPS/ALPS like affected subjects. Conversely, the reduction of at least of one class of was documented in all (100%) patients with a clear CVID phenotype as expected, while was shown in 50% and in 17% of patients respectevely affected with ALPS/ALPS like and citopenia (p=0.003). Lymphocytopenia at last FUP was observed in 46% of cytopenia subgroup, in 17% of ALPS/ALPS like group and in 40% of CVID affected subjects (p=ns). The impact of the type of TACI variants on hypogammaglobulinemia and/or lympocytopenia was not evident. Summary/Conclusion: In the present study, TACI variants studied in a cohort of patients affected with cytopenia and ALPS/ALPS like disorders are found in around 10 % of the subjects. The immune-dysregulation expressed by the described phenotype found in TACI the probable explanation. Unexpectedly in a high proportion of the subjects the typical immunological features of CVID including immunoglobulin and lymphocyte count depletions are not found. This observation encourages the application of diagnostic panels including TACI variants considering in ALPS/ ALPs like syndrome or of chronic/refractory cytopenias. These findings would surely deserve confirmation in prospective studies composed by larger numbers of patients.Keywords: Bone marrow failure